• Journal of Power Electronics
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• v.13 no.6
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• pp.939-954
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• 2013

The Direct Torque Control (DTC) technique for Permanent Magnet Synchronous Motors (PMSM) is receiving increased attention due to its simplicity and robust dynamic response when compared with other control techniques. The classical switching table based DTC results in large flux and torque ripples in the motors. Several studies have been reported in the literature on classical DTC. However, there are only limited studies that actually discuss or evaluate the classical DTC. This paper proposes, novel switching table / DTC methods for PMSMs to reduce torque ripples. In this paper, two DTC schemes are proposed. The six sector and twelve sector methodology is considered in DTC scheme I and DTC scheme II, respectively. In both DTC schemes a simple modification is made to the classical DTC structure. The two level inverter available in the classical DTC is eliminated by replacing it with a three level Neutral Point Clamped (NPC) inverter. To further improve the performance of the proposed DTC scheme I, the available 27 voltage vectors are allowed to form different groups of voltage vectors such as Large - Zero (LZ), Medium - Zero (MZ) and Small - Zero (SZ), where as in DTC scheme II, all of the voltage vectors are considered to form a switching table. Based on these groups, a novel switching table is proposed. The proposed DTC schemes are comparatively investigated with the classical DTC and existing literatures through theory analysis and computer simulations. The superiority of the proposed DTC method is also confirmed by experimental results. It can be observed that the proposed techniques can significantly reduces the torque ripples and improves the quality of current waveform when compared with traditional and existing methods.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.314-316
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• 2006

In this paper, the plastic organic thin-film transistors (OTFTs) with $32{\ast}32$ array are presented. Flexible organic light emitting diodes (OLEDs) operated by OTFTs are fabricated with a novel lamination method and the results are also presented. OTFT pixels defined by photolithography, and pentacene deposited by thermal evaporation. Fabrication method and the performances of green PHOLEDs with high efficiency, stability, and electrical performance are discussed.

• Genomics & Informatics
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• v.17 no.3
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• pp.34.1-34.3
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• 2019

Direct-to-consumer (DTC) genetic testing is a controversial issue although Korean Government is considering to expand DTC genetic testing. Preventing the exaggeration and abusing of DTC genetic testing is an important task considering the early history of DTC genetic testing in Korea. And the DTC genetic testing performance or method has been rarely reported to the scientific and/or medical community and reliability of DTC genetic testing needs to be assessed. Law enforcement needs to improve these issues. Also principle of transparency needs to be applied.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1202-1205
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• 2006

Dynamic Driving Carbon Nanotube Backlight Units (CNT-BLUs) can well utilize the persistence of their phosphor. This paper studies several dynamic driving schemes for the CNT-BLU developed by DTC/ITRI. Their illuminating efficiencies are experimentally evaluated. From these evaluations, this paper develops a new driving approach and even better efficiencies are obtained.

• Journal of Power Electronics
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• v.17 no.1
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• pp.161-171
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• 2017

To enhance the reliability of two-motor drive systems, this paper proposes an improved direct torque control (DTC) scheme (P-DTC) for five-leg dual-PMSM drive systems. First, the topology of a five-leg dual-PMSM drive system is illustrated. To clarify the analysis of the P-DTC, the standard DTC scheme for three-phase drive systems is presented. The operation of a five-leg dual-PMSM drive system is classified into three situations according to the definitions of the switching-vector unions. Compared with the existing DTC scheme (R-DTC), the P-DTC can minimize the replacement of active switching-vectors to zero switching-vectors. When this replacement cannot be avoided, the P-DTC uses a proposed master-slave selection principle to minimize the system error. Comparing with the R-DTC, the P-DTC has lower torque ripples, a wider speed range and a faster torque increasing response. Experiments have been carried out in the coupling and independent modes, and the effectiveness of the P-DTC is verified by the obtained results.

• Journal of IKEEE
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• v.23 no.2
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• pp.628-635
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• 2019

This paper proposes sliding mode control (SMC) method for improvement of dynamic response for IPMSM based on DTC with constant switching frequency. DTC with constant switching frequency method consists of PI torque controller and triangular comparator for constant torque error status. It has the poor dynamic response compared to conventional DTC. This paper proposes improvement method of dynamic response of DTC with constant switching frequency by using SMC. Simulation results confirm the effectiveness of the proposed method.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.4
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• pp.268-277
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• 2009

This paper presents an DTC-PWM (Direct Torque Control-Pulse Width Modulation) of PMSM (Permanent Magnet Synchronous Motor). The proposed DTC-PWM method combines a conventional DTC and PWM approach for switching signal generation. The actual torque is estimated by the torque estimator in conventional method, but the switching signal is generated by PWM method according to the switching rules and torque error. A effective voltage vector and zero vector are used to generate the switching signals and asymmetric switching method is applied. A simple calculation of PWM without any complex determination of space vector can assure the constant switching frequency with an constant torque and flux. The proposed torque control scheme for PMSM is verified by experimental results.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2162-2172
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• 2016

This paper presents a Direct Torque Control (DTC) strategy for the five-phase induction motor driven by a three-level five-phase inverter in order to improve the performance of the five-phase induction motor. In the proposed DTC technique, only 22 voltage vectors out of 243 available voltage vectors in a three-level five-phase inverter are selected and are divided in 10 sectors each with a width of $36^{\circ}$. The four different DTC combinations (DTC-I, II, III and IV) for a three-level five-phase induction motor drive are investigated for improving the performance of five-phase induction motor. All four of the DTC strategies utilize a combination of the same large and zero voltage vectors, but with different medium voltage vectors. Out of these four techniques, DTC-II gives the best performance when compared to the others. This DTC-II technique is analyzed in detail for improvements in the performance of five-phase induction motor in terms of torque ripple, x-y stator flux and Total Harmonics Distortion (THD) of the stator phase current when compared to its two-level counterparts. To verify the effectiveness of the proposed three-level five-phase DTC control strategy, a DSP based experimental system is build. Simulation and experimental results are provided in order to validate the proposed DTC technique.

• Journal of Power Electronics
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• v.12 no.6
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• pp.895-903
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• 2012

This paper presents a fast switching direct torque control (FS-DTC) using only a single DC-link current sensor. In FS-DTC, six new active voltage complex space vectors (CSVs) are synthesized by the conventional active voltage space vectors (SVs). The corresponding sectors are rotated in the anticlockwise direction by 30 degrees. A selection table is defined to select the CSVs. Based on the "Different Phase Mode", the output sequence of the selected CSV is optimized. Accordingly, a reconstruction method is proposed to acquire the phase currents. The core of the FS-DTC is that all of the three phase currents can be reliably reconstructed during every two sampling periods, which is the result of the fast switching between different phases. The errors between the reconstructed and actual currents are strictly limited in one sampling period. The FS-DTC has the advantages of the standard DTC scheme such as simple structure, quick torque response and robustness. As can be seen in the analysis, the FS-DTC can be thought of as an equivalent standard DTC scheme with 86.6% of the maximum speed, 173.2% of the torque ripple, and 115% of the response time of the torque. Based on a dSPACE DS1103 controller, the FS-DTC is implemented in an induction machine drive system. The results verify the effectiveness of the FS-DTC.

• International journal of thyroidology
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• v.10 no.2
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• pp.96-101
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• 2017

Background and Objectives: Anaplastic thyroid carcinoma (ATC) is commonly related with concurrent differentiated thyroid carcinoma (DTC). We aimed to examine the clinicopathologic characteristics, prognosis and gene expression of DTC with anaplastic foci. Materials and Methods: Eighteen patients with DTC with anaplastic foci were enrolled in this study. To compare the clinicopathologic characteristics and prognosis of anaplastic foci subjects with conventional ATC or DTC, we additionally included 12 ATC and 1030 DTC patients who diagnosed during same period. Immunohistochemistry was performed to check the gene expression in anaplastic foci and DTC component. Results: In anaplastic foci group, tumor size was larger ($2.5{\pm}1.3$ vs. $1.2{\pm}0.9cm$, p=0.001), distant metastasis was more frequent (11.1 vs. 0%, p=0.000) and 1-year survival rate was low (88.9 vs. 100%, p=0.000) than DTC group. In contrast, compared with ATC group, anaplastic foci group showed younger age at diagnosis ($50{\pm}16$ vs. $63{\pm}18years$, p=0.039), smaller tumor size ($2.5{\pm}1.3$ vs. $3.8{\pm}1.4cm$, p=0.027), less distant metastasis (11.1 vs. 41.7%, p=0.084) and longer 1-year survival rate (88.9 vs. 25.0%, p=0.001). Expression of p53 protein was observed in 100% of anaplastic foci, ATC and 12.5% of papillary thyroid carcinoma component. Conclusion: DTC with foci of anaplastic transformation has a worse prognosis than DTC, but a better prognosis than ATC. Our results support that DTC with anaplastic foci was intermediate state from DTC to ATC.